Temperature and strain rate effects on the strength and ductility of nanostructured copper

We show that the yield strength for Cu with ultrafine grain sizes becomes obviously temperature and strain-rate dependent, in contrast to the temperature/rate insensitive behavior of conventional face-centered-cubic metals. A thermally activated deformation mechanism is operative at room temperature and especially at slow strain rates, but not at 77 K. In addition to the gain in strength, the tensile ductility and particularly uniform strains also increase at cryogenic temperatures and with increasing strain rate, as a result of improved strain hardening due to suppressed dynamic recovery. (C) 2003 American Institute of Physics.